The present invention relates to helical cutting tools, particularly to the type having helical arrays of cutting inserts removably attached to seats formed in the cutting tool.
The conventional helical cutting tool of this type usually includes a plurality of helical arrays of cutting inserts, in which the helical angle is relatively small, being usually from 10.degree. to 25.degree., and in which the cutting edge of each insert is axially spaced from the cutting edge of the next adjacent insert. The inserts of each helix are thus in staggered relationship such that two (or more) rows of inserts are necessary to produce one complete cutting edge. Accordingly, a cutting tool having four helical arrays of cutting inserts effectively produces two complete cutting edges.
In such conventional cutting tools, the cutting edges of the inserts are in direct contact with the workpiece for a relatively small proportion of the surface of the cutting tool embraced by the workpiece. For example, in a typical helical cutting tool having four helical rows of inserts disposed at a helical angle of 15.degree., the cutting edges of the inserts are in direct contact with the workpiece for only about 25% of the semi-cylindrical surface of the cutting tool embraced by the workpiece during the cutting operation. This results in significant chattering, hammering and vibration during the cutting operation. Moreover, it permits relatively low workpiece feed, because the workpiece feed rate depends on the number of effective complete cutting edges, rather than on the number of helical rows of cutting inserts, included in the tool.
An object of the present invention is to provide a helical cutting tool having advantages in the above respects.